‘Monkey archaeology’ reveals macaque’s own Stone Age culture

The world’s first archaeology dig of an old world monkey culture has uncovered the tools used by previous generations of wild macaques – a group of primates separated from humans by some 25 million years of evolution.

Only a few decades ago scientists thought that humans were the only species to have worked out how to turn objects in their environment into useful tools. We now know all sorts of animals can do the same – but the tools of choice are usually perishable materials like leafs and twigs.

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This makes the origin of these behaviours difficult to study, especially when you consider that the record of hominin stone tool use stretches back more than 3 million years.

Michael Haslam of the University of Oxford and his team conducted their dig on the small island of Piak Nam Yai in Thailand, one of the islands where these monkeys live and use stone tools (see video above). They dug through the sandy sediments at the site and found 10 stone tools attributed to macaques, based on their wear patterns.

By dating the oyster shells found in the same sediment layers, they determined the tools could be as old as 65 years, going back two macaque generation.

We know from eyewitness accounts that these monkeys have been using tools for at least 120 years, so the study doesn’t push the age of the behaviour back. But Haslam sees it as a first step towards digging deeper into the origins of the behaviour.

Chimpanzee dig

A long record of ancient stone tools could tell us if the monkeys picked up tool use in response to an environmental stress, such as rapid sea level changes, for example. And it might even show how the practice may have been transferred between different island populations.

Just 150 years ago, archaeologists’ claims about early human stone tools were met with scepticism, Haslam says. Since then, scientists have created a detailed and incremental record that shows how hominin stone technologically advanced over millions of years of innovation.

“We’re at year zero for the primate world,” he says. It may one day be possible to address questions about how and why tool use arises in animal populations, and about the extent to which that kind of behaviour is – or isn’t – uniquely human, he adds.